In the construction of liquid crystal display (LCD) panels, a method of illumination must be utilized since the liquid crystal itself does not illuminate. The illumination is also important when the available lighting for viewing a LCD is insufficient. In order to make large LCD panels, and specifically colored LCD panels, a high efficiency light source must be used for illumination in order to achieve the requirements of small panel thickness, lightweight and low power consumption. The capability of achieving high brightness at a low power consumption is essential for obtaining a long battery life between recharging in portable applications for LCD. In recent years, the improvements made in the other parts of a LCD display, i.e., the color filter arrays, the thin film transistors, and other performance enhancement layers reduce the overall transmittance of a liquid crystal display panel. As a result, any improvement that can be made in the brightness/power ratio must be obtained from the improvement in the backlighting efficiency of a panel.
In the conventional backlighting technology for flat panel displays, cathode fluorescent lamps are frequently used to illuminate the flat panel display. The cathode fluorescent lamps provide the benefits of high luminous efficiency, long service life, lightweight and rugged structure. The lamps are normally installed in pairs along the sides of a display panel, e.g., a display panel in a notebook computer, with a light tube arrangement for creating uniform lighting across a diffuser screen. More recently improvements in backlighting have been provided which include a flat fluorescent backlight and a wedge-shaped light tube which distributes the light from a single bulb evenly over the entire display surface. The wedge-shaped construction allows a single lamp to illuminate the entire liquid crystal display panel. A plastic molded light tube which contains prismatic specular reflectors helps to spread the light uniformly across a front plane of the device.
The flat fluorescent lamp which has also been recently developed is used to directly illuminate a display panel. A typical construction of a flat fluorescent lamp device measures only 3 mm thick. Panel sizes ranging from diagonal lengths between 25 mm and 350 mm have been made by using the conventional cold cathode technology. The lamp housing can be constructed by using a formed plate and a flat plate laminated together. For instance, a typical lamp can be constructed of a serpentine channel of four intervals equipped with an electrode at each end. A typical design of the flat fluorescent lamp includes a phosphor coating on both a top and a bottom plate, while a reflective coating is placed only on the bottom plate. A high voltage of between 1 kV and 3 kV (depending on the panel size and cathode type) is normally required to operate a flat fluorescent lamp.
For a color liquid crystal display device, color filters in three basic colors of red, green and blue must be utilized. The manufacturing process for color filters involves a number of steps such as chemical vapor deposition, spin coating of insulators and metals, and the planarization and orientation film coatings. Color filters can be formed on glass substrates by complicated processing steps which include glass finishing and preparation of both the front and the back of a substrate, the polishing and lapping process, the washing and cleaning of the substrate, the coating, curing and other steps which must be performed on the substrate.
The formation of color filters requires a repetitive process to be carried out for forming the three primary color elements. In between the color elements, a black border or a black matrix is needed for providing the necessary contrast. To prepare the color filters, either an organic dye or a pigment can be used as long as it is suitable as a light absorbing color filter material. For instance, a gelatin can be deposited and dyed in successive photolithographic operations by using proximity printing equipment and standard photoresist materials. A pigment dispersion method can also be used which eliminates the gelatin layer and is capable of higher temperature stability. Other methods for forming color filters include electrodeposition and printing.
FIG. 1A shows a conventional color filter device 10 consisting of three primary color filters, i.e., red filter 12, green filter 14 and blue filter 16. A white light source 20 is used for backlighting the single pixel 10. In this conventional color filter/backlighting arrangement, a large area is occupied by a single pixel and as a result, the resolution achieved on a liquid crystal display panel is relatively poor.
In another conventional color filter/backlighting device 22, as shown in FIG. 1B, in the same area that was occupied by a single pixel where a white light backlighting is used, three pixels are arranged wherein each pixel can be one of the three primary colors by utilizing three different light sources 24, 26 and 28 for each pixel. Significantly improvement in resolution is therefore possible due to the greatly reduced sizes of the pixels. The color filters used in this arrangement, 30, 32 and 34 are essentially transparent for accepting a color from the color sources 24, 26 and 28. This arrangement is known as a sequential color display. In the sequential color display arrangement, a cathode-ray tube is normally employed as a light source that emits light at a plurality of wavelengths. Since there is an inherent light loss created by the polarization of the emitted light and the duty cycle of the liquid crystal cell, the maximum efficiency for the transmitted white light is reduced to as low as 25%. The display brightness in a field sequential color display is therefore a major concern.
It is therefore an object of the present invention to provide a flat fluorescent color lamp for liquid crystal display panel illumination that does not have the drawbacks and shortcomings of the conventional backlighting devices and color filters.
It is another object of the present invention to provide a flat fluorescent color lamp for liquid crystal display illumination that performs both the functions of a color filter and a backlight source.
It is a further object of the present invention to provide a flat fluorescent color lamp for liquid crystal display panel illumination by utilizing a lamp body constructed of serpentine-shaped channels for exhibiting the three primary colors of red, green and blue in at least one of such channels.
It is another further object of the present invention to provide a flat fluorescent color lamp for liquid crystal display panel illumination by utilizing a lamp body formed in a sintering process by glass powder, binder powder and a solvent which has at least three serpentine-shaped channels each exhibiting a primary color of red, green or blue.
It is still another object of the present invention to provide a flat fluorescent color lamp for liquid crystal display panel illumination by providing a lamp body constructed of at least three serpentine-shaped channels each filled with a fluorescent powder for exhibiting one of the three primary colors of red, green and blue when the powder is energized by an electrical charge.
It is yet another object of the present invention to provide a flat fluorescent color lamp for liquid crystal display panel illumination by providing a lamp body that is divided into at least three serpentine-shaped channels and equipping each channel with a pair of spaced apart electrodes.
It is still another further object of the present invention to provide a flat fluorescent color lamp for liquid crystal display panel illumination by providing a lamp body that is divided into at least three serpentine-shaped channels each filled with a gas capable of emitting ultraviolet energy to energize a fluorescent powder contained in the channel.
It is yet another further object of the present invention to provide a method for the color illumination of liquid crystal display panels by using a lamp body constructed of at least three serpentine-shaped channels each filled with a fluorescent powder and is capable of being energized by a gas filling the chamber to exhibit one of the three primary colors of red, green and blue.